Polymers of cyclic dimers of diolefins as plasticizers for oil resistant elastomers



Patented May 22, 1951 POLYMERS OF CYCLIC DIMERS OFDIOLE- FINS AS PLASTIGIZERS FOR OIL RESIST- ANT ELASTOMERS Albert M. Gessler, Cranford, N. J., assignor to Standard Oil Development Company, a corporation of Delaware No Drawing. Application June 16, 1948, Serial No. 33 143 This application is a continuation-in-part of copending application Serial No. 719,637, filed on December 31, 1946, now Patent No. 2,545,516, March 20, 1951.

4 Claims. (Cl. 260-23) polymer on contact with gasoline, thereby discoloring the latter. These undesirable properties disqualify this type of cheap plasticizer from use with .GR-A type rubbers where light-colored com- The present invention relates to synthetic rub- 5 pounds are required or where a discolored extract ber'compositions and particularly to improved, cannot be tolerated on contact of the plasticized plasticized, diolefin-acrylonitrile copolymer compolymer with gasoline. positions and a method of preparing the same. Where light-colored articles were desired, such Synthetic rubber materials prepared by the coas bowl scrapers, bath mats, gasoline hose, autopolymerization of a conjugated diolefin such as mobile matting and panelling, floor tile, whitebutadiene-1,3 anda nitrile such as acrylonitrile wall tire compounds, medical supplies, dairy in aqueous emulsion have achieved considerable equipment, sealing members for food packaging commercial importance particularly in view of and similar specialty products, the rubber industheir oil-resistant properties. The superiority in try was forced heretofore to rely on plasticizing oil resistance of these copolymers over natural agents which not only acted as solvents for the rubber has permitted them to compete with and GR-A type polymers, but in addition such agents even displace natural rubber despite the fact that had to be substantially colorless. the cost of these copolymers has been greater The plasticizers most commonly used for the than that of natural rubber. aforementioned specialty products have been di- A major, difficulty encountered with all synallgyl phthalates such as dimethyl, diethyl, ditheticrubbers of the butadiene type has been the butyl, or dioctyl ,phthalates, dialkyl esters of difact, that they are in general relatively hard, dry carboxylic aliphatic acids such as dibutyl sebaand non-tacky materials and, unlike natural rubcate, and phosphoric acid esters such as tricresyl her, they are incapable of being masticated to a phosphate or tributoxy-ethyl phosphate. Howsoft, plastic condition which is not only desirable ever, thepreparation of the aforementioned orbut necessary for proper compounding and procganic chemicals. usually involves a more or less essing int the desired articles, complexchemical synthesis, and hence the chem- In order to overcome this difficulty, it has-been icals themselves are about 10 times as expensive necessary to add softeners or plasticizers'to these as theudarkreolqred coal-tar plasticizers mensynthetic rubbery materials thereby improving tioned previously. Since the plasticization of their compounding and processing characteris- GR-A. type elastomers requires relatively large tics. The selection of suitable softeners, particuproportions of plestieizing agent, 6- 3 to 40 or larly for diolefin-nitrile type synthetic rubbers ore parts by wei h p 100 Parts Of the e has presented av number of serious difficulties tOmeIS, it l be rea y appreciated h the use since their properties are so radically different of the above-named organic Ch i s as P from natural rubber that many materials which CiZeTS becomes prohibitive Where -p c d 9 are compatible with or exert a substantial plastit cleS are to be manufactured. Ac o d y the cizing efiect upon natural rubber or other rub- 1165 Of p e a tOmB S has been heretofore .bery hydrocarbons such as butadiene-styrenecorgely restricted to h-p d quality p polymers are incompatible with or do not effect 40 eiedlty a s, 0 low-Priced a ti les wherein any improvement i th s ft ss or plasticity of the use of coal-tar plasticizers could be tolerated diolefin-nitrile type synthetic bb r despite the previously described disadvantages of In order to plasticize diolefin-nitrile elastomers, e lattelfi which are known technically under the generic In the op n nsappfic i n SeTieJ1N0-719fi3'7 t of 33 type rubbers, th t has genemny the new basic concept applicable to the plasticizsought out those materials which arecompatible hg of GR-A ela m s Was described th0r011gh1y with said rubbery GR-A type copolymers or are and need ot be repeated here. This concep w t or sweuing agents theref r. ofiers a highly successful alternative to the use of A number of cheap solvent-type plasticizers are the for mentioned expensive chemicals and conavailable for increasing the softness or apparent s s o us plasticizers which, though co p elasticity of these copolymers. However, all of ihle, re inherently imm scible W t the p y these cheap plasticizers are coal-tar oils or other to be p ast c e aromatic coal-tar derivatives, are dark brown to It has now been discovered that viscous polyblack in color,.cause lacing on the mill and are mers of diolefins having 4 to 5 carbon atoms, therefore relatively difiicult to mill into GR-A such as poly t n polyisoprene 01 po p type polymers; furthermore while these plastiperylene, or of the respective cyclic dimers therecizers do increase the softness of the polymers, of, are particularly effective for plasticizing nitrile they do not improve greatly the processing or exrubber when these polymers are of a molecular trusion properties thereof and finally they are weight which is high enough to prevent bleeding relatively freely extracted from the plasticized of the plasticizer from the plasticized composition and low enough to make the plasticizer compatible and coherent with the polymer to be plasticized. The desired molecular weight range of the herein claimed polymeric hydrocarbon plasticizers appears to lie within the limits of (8000) to (20,000) or preferably (10,000) to (15,000), as determined by the Staudinger method.

The viscous polymers can be prepared by any of the known methods including emulsion poly merization described for example in copending U. S. patent application Serial No. 637,782, filed on December 28, 1945, by P. K. Frolich et al. now Patent No. 2,500,983, March 21, 1950; sodiumcatalyzed mass polymerization; or by peroxide catalyzed mass polymerization, the details of which are described for example in copending U. S. patent application Serial No. 782,850, filed on October 29, 1947, by E. Arundale et al. Instead of the polymers prepared by any of the aforementioned methods, an excellent plasticizer can be obtained by thermally polymerizing dimers of conjugated C4 to C5 diolefins such as butadiene or piperylene according to the method the details of which are described in copending U. S. patent application Serial No. 638,589, filed on December 31, 1945, by M. W. Swaney et a1. now Patent No. 2,513,244, June 27, 1950. Furthermore, instead of polymerizing a diolefin such as butadiene by itself, it can be advantageously copolymerized with a vinyl aromatic hydrocarbon such as styrene, alpha-methyl styrene, para-methyl styrene, or alpha-methyl-para-methyl styrene, or the corresponding ethyl styrenes, vinyl naphthalene and the like.

One convenient method of preparing the desired plasticizers comprises placing the following charge in a one-quart pressure bottle:

Grams Water 400 Butadiene 200 Sodium soap Potassium persulfate 0.6 Di-isobutylene mercaptan 8 it with the latex of the nitrile rubber to be plasticized, whereafter the mixed latex is coagulated; or the latex of oily polymer may be coagulated separately and the resulting oily polymer can be subsequently mixed into separately coagulated nitrile rubber mechanically on a rubber mill or in an internal mixer.

The aforementioned recipe can of course be varied by substituting known equivalents for the ingredients mentioned. For example, isoprene can be used instead of butadiene; the soap may be any alkali metal or ammonium soap of a. higher fatty acid having 6 to 18 carbon atoms such as caproic, stearic, palmitic or linoleic; or it may be a synthetic soap such as an alkali sulfonate, alkyl aromatic sulfate, etc.; other known oxygen yielding catalysts such as benzoyl peroxide or cumene hydroperoxide can be used instead of the alkali persulfate; and mercaptans having 6 to 16 carbon atoms, notably a commonly available mixture of aliphatic mercaptans consisting predominantly of dodecyl mercaptan can be used in place of the di-isobutylene mercaptan.

EXAMPLE I A set of runs was carried out to evaluate the ease and speed with which Perbunan could be plasticized by polybutadiene oils.

The polybutadiene oils were added on a 6" x 12" mill to Perbunan having 26 weight percent of combined acrylonitrile and 74 weight percent of combined butadiene. The starting temperature was controlled between 90 and 100 F., and cooling water was supplied to the rolls during the mixing. The Perbunan was broken down before any additions were made by passing it six times through the mill set at 0.007". The blends which were prepared and the time required to add a given amount of plasticizer are listed in Table I below. A control compound with dibutyl phthalate is included.

Table I Type of Plasticizer Parts of Plasticizer For 100 Parts of Perbunan-26 Time to add Plasticizer Remarks Polybutadiene nique) Int. Vis. 0.456.

8 do (in Dibutyl Phthalate (polymerized by emulsion method) Intrinsic Vis. 0.134. Polybutadiene (polymerized by SOdllllIl techilgggi tadiene (mass polymerizedfIn t. Vis.

do Polymerized Vinyl Oyclohexene 3 Minutes 9 Initial addition diflicult.

18 Initial addition very dimcult. Mixed stock bags.

10 1 No difficulty. Easy blendmg. 20 2% Do.

5% Initial addition slow.

20 D0. 10 N o difiiculty. Easy blend- Do. Do.

1 Intrinsic viscosity I=1n N [0, where N is the relative viscosity, i. e., the ratio oi the viscosity of the polymer solution to the viscosity of the solvent (di-isobutylene at 25 0.), and where C is the concentration of the polymer solution expressed in grams of polymer per 100 cc. of solution. Knowing the intrinsic viscosity I, the molecular weight M of the polymer can then be calculated from the following formula:

2 This material was a cyclic butadiene dimer further polymerized by thermal mass synthesis at 280 C. 300 C. for 24 hours, the oily polymer being recovered from the viscous, resin-containing polymerization product by extraction with methyl ethyl ketone.

The bottle containing this charge is placed on a rotating wheel in a water bath maintained at C. and mixed for 20 hours. The reaction mixture is finally short-stopped and unreacted butadiene stripped off with live steam. The resulting latex of the oily polymer can be used As has been pointed out previously, the ease with which plasticizer may be added to a polymer on the mill is dependent on the viscosity of the plasticizer. With fluid liquids, addition is difficult and must be made intermittently and slowly to avoid breaking the formed band. As

directly as to eiiect the plasticizing' by mixing the viscosity of the plasticizer is increased bemore diificult to incorporate with the polymer than miscible plasticizers. At the semi-solid state mentioned above, there is no significant difference in the rate at which the two types of plasticizer can be mixed with the polymer.

These facts are substantiated by the data in Table I. The long mixing times required with the fluid miscible plasticizer, dibutyl phthalate, in run No. l and with the low viscosity polybutadiene oil in run No. 2 are typical examples.

After incorporation of the dibutyl phthalate,

the stock was still highly elastic. The band around the roll was knurled and the bank only moderately active. When out from the mill the stock shrank rapidly to form a chunk rather than a sheet of rubber. In contrast, in every case with the immiscible polybutadiene oils, the stocks were characterized by greatly diminished elasticity such as is highly advantageous for extrusion, calendering, molding, etc. Smooth bands 5 weights measured. From the specific gravity of the stock and from the measurements of weight and length taken, the unit volume, in cubic centimeters per linear inch, was calculated for each tube.

A material, if it were purely plastic, would extrude to die dimensions and would have, under the conditions employed here, a unit volume of 0.90 cubic centimeter per inch. This value, therefore, may be taken as the ideal value representing the most desired case of purely plastic behavior. However, elastic tendencies of high polymer systems result in tube volumes which are greater than the ideal value, the difference between the actual and ideal tube volumes being proportional to the degree of elasticity present. It is thus possible to relate processibility to the stock swell at the die of the extruder. This has been done for the plasticized blends shown in Table I. The data, which include the results obtained from a sample of broken-down Perbunan without any added plasticizer, and from a series of Perbunan-polyisobutylene plasticizer (12,000 Staudinger molecular weight) systems are shown in Table 11.

Table II Plasticizer Elast1c i gf Per Cent Change of Rate f Swell Swen Natural Swell Extrusio Run (Volume of (Based on 2.67 cc./

Parts Per (Based on Inches No. Extruded inch olume of 100 Parts Ideal Vol- Per Type of Pen Tube in mm OH) 90 Non-Plasticized Minute bunamzfi ccJInch) m/incfi) Perbunan-26 1 None None 2. 67 195 30 2 Dlbutyl Phthalate 10 3. 49 287 +30.7 (Increase) 35. 5 3 do 20 3. 39 277 +27.0 (Increase)..... 38

30 3. 36 273 +25.9 (Increase) 40. 5 40 3. 28 265 +22.9 (Increase) 43 0 134 10 1. 94 115 27.3 (Reduction). 72 rt i g imdiene Int. 10 2. 00 12.3 -25.1 (Reduction) 47 3 ldol 20 1.80 100 -32.6 (Reduction) e4 9 do 40 1. 64 83 38.6 (Reduction) 10. Pglgtlsisutadiene Int. Vls 10 1.88 110 29.6 (Reduction).. 51 11 ldo: 20 1. 52 70 43.0 (Reduction) s2 12 do 40 1. 4 56 46.7 (Reduction)- l3. Ptillymerized Vinyl Cyclo- 10 1.68 87 37.0 (Reduction) 92 20 1. 52 70 43.0 (Reduction) 02 30 1.44 60 -46.0 (Reduction) 96 40 1.4 56 46.7 (Reduction) 97 10 2. 04 128 23.6 (Rcduction) 53 20 1. 80 100 32.6 (Reduction). 63 30 1. 89 36.2 (Reduction). 71 40 1.50 67 -43.7 (Reduction) 77 without surface irregularity 'or rugosity were formed around the mill roll. The bank was extremely active and the stock when out from the mill formed smooth sheets, a result realized from the lessened tendency for elastic shrinkage.

EXAMPLE II lected and taken directly to an air circulating From Table II it can be seen that the poly butadiene oils are even more effective processing aids for Perbunan than polyisobutylene. The elasticity of the prepared blends decreases sharply with polybutadiene concentration and the stocks soon approach the range of excellent processing performance. By contrast the increase in elasticity shown for the dibutyl phthalate blend is typical of the behavior of miscible plasticizer systems, once again emphasizing the fact that while miscible polymers are useful to increase the softness, 1. e., reduce the force required to cause a given deformation of the raw plasticized composition, they actually tend to aggravate the elastic swell on extrusion and similar processing operations requiring a shaping or deformation of the composition.

In contrast, the immiscible plasticizers actually cause an extremely favorable reduction of elastic swell or spring-back, as is illustrated especially clearly-in the penultimate column of figures in Table 11. These figures show that compositions plasticized in accordance with the present invention exhibit an elastic swell which is a mere fraction, e. g, 20 to 50% of the corresponding swell of the non-plasticized basic nitrile polymer whereas miscible plasticizers bring about an elastic swell which is actually larger than the swell of the non-plasticizednitrile polymer. The effect of the polymerized vinyl cyclohexene is particularly striking at concentrations between and 20 percent, the reduction of elastic swell at percent concentration of this last-named polymeric plasticizer being not only far below anything achieved by any other known plasticizer, but also substantially below the values obtained by using the other types of polybutadiene oils in accordance with the present invention. No explanation for this unusual effectiveness is available as yet polymer at low concentrations isonce again outstanding.

Other things being the same, the-volume of the tube extruded from any stock increases as the rate of extrusion is increased. From this fact, it is all the more surprising that, with the immiscible systems now discovered, the unit equilibrium volume of the tube is decreasing sharply at the same time that the rate of tube exit is 10 increasing so rapidly.

EXAMPLE III Using a convention mechanical goods formulation, a number of Perbunan vulcanizates was 5 prepared with the polybutadiene oils to determine the effect of these oils on vulcanizate quality. These compounds, along with two controls, are shown in Table III. Also included are the-data from a few routine tests carried out with these vulcanizates.

Table III Compound Perbunan-ZG Dibutyl Phthalate 0 34) Polybutadiene (I. V. 0.456) Polybutadiene (I. V. 0.368) Polymerized Vinyl Gyclohexene Zinc Oxide Stearic: Acid Semi-Reinforcing Black (Gas Sulfur Benzothiazyl Disulfide Tensile-Elongation, Modulus 300$}, Cured at 287 F.:

2 710 590 1, 0 200 1, 205 ASTM #3 Oil at- Rocm temperature 57. 6 42. 5 87.6 100. 8 111.2 75. 5 300 F 26. 7 10. 5 58. 4 86. 0 87. 4 41. 5 ASTM #1 Oil at- Room temperature 11.2 6. 4 20. 4 26. l 28. 8 l7. 8 30 0.3 10. 8 5. 3 10. 4 11.8 3. 2 Thiokol Bend Test OK at Broke at OK at Broke at 0 at Broke at -80F 75 80 F 75 SO F. 55 F though there are certain indications from runs employing butadiene-styrene copolymer oils that aromatic rings in the polymer chain of the plasticizer may tend to accentuate its beneficial effect on processing characteristics.

Another important advantage is brought out by a consideration of the data contained in the last column of Table II. The factory compounder must have stocks which are plastic so that he can shape them, prior to vulcanization, into useful articles. In addition, because the rubber industry is highly competitive, he must have compounds which process rapidly. The great advantage which the immiscible systems enjoy in this respect is shown by the extrusion rate data of Table II where the rate of tube exit from the extruder, based on equilibrium specimen dimensions (i. e., dimensions after substantially total release of elastic stresses) is expressed as a function of the plasticizer concentration. With dibutyl phthalate only moderate increase in extrusion rate is realized. With the polybutadiene oils and polyisobutylene, the rate of tube exit increases rapidly with plasticizer concentration and very soon reaches a value two to three times that of the original. The very sharp increase in extrusion rate obtained with the vinyl cyclohexene From the tensile data in Table III it is seen that good vulcanizate quality can be obtained with polybutadiene oils. When the moduli for each vulcanizate in the table are graphed as a function of the time of cure, it appears that the polybutadiene oils in compounds Nos. 3 and 4 are approximately equivalent to dibutyl phthalate in efiect 0n cured properties. With the polybutadiene oils of compounds. Nos. 5 and 6 the vulcanizates are characterized by lower modulus. However, it should be observed that this effect in the case of compound No. 5 is not related to cure low apparent swell obtained with the vulcanizate containing dibutyl phthalate is caused by extraction of the plasticizer from the vulcanizate. The sharp differences in the magnitude of swell of the compounds with the various polybutadiene oils is probably a result of difierences in the covulcanization and extraction tendencies of'the polybutadienes'.

From the Thiokol Bend Test data, it is appar= ent that vulcanizates with attractive low temperature properties may be prepared from the polybutadiene' oils.

EXAMPLE IV 1. Perbunan-35 (butadiene' acrylonitrile emulsion copolymer) Mooney viscosity at 212 F.; 2 min. Acrylonitrile content of polymer per cent 37.1 Solids content of latex do 24.3

2. Polybutadiene oil (intrinsie vis. 0.4)

Mooney viscosity at 212 FL; 2 min. 41 Polymer content of latex per cent 25 660 parts by weight of latex #1 was blended with 160 parts of latex #2 and the pH of the resulting: mixture was adjusted to 8.8 by theaddition of a small amount of 1. N NaOI-I'. The final latex was creamed by the addition of 0.8 volume of 26% NaCl solution per volume of latex, the brine being added to the latex. The particle size of the coagulate was adjusted by the addition of about 80 cc. of 1% acetic acid. Theliquor was then filtered from the coagulate and the polymer was then-slurriedin distilled water to remove residual inorganic salts. After filtering. and slurrying a second time the final washed coagulate was filtered to a Water content of about 50% .and then dried in a circulating air oven for 8 hours at 175 F. The final polymer blend resulting from this coprecipitation method had the following analysis:

Acrylonitrile content per cent; 29.? Mooney viscosity at 212 F.; 2 min 60 The processing characteristics of this coprecipitated polymer blend were determined according to the extrusion test described in Example II. The results obtained Were as follows:

Extrusion rate 72 inches/min. (154 grams/min.) Extrusion volume 1.867 cc./inch When compared with the data of Table II, these figures show the excellent effectiveness of thismethod of plasticizing by coprecipitating the principal polymer with the plasticizer in latex form. The present results are particularly remarkable when the fact is taken in account that the nitrile polymer used in this example had about 37% of combined nitrile, thereby being especially tough and immiscible, whereas the nitrile polymer used in the series of runs summarized in Table II had only about 26% of combined nitrile and was correspondingly more workable to begin with.

The properties of the coprecipitated polymer blend in vulcanized state are also very gOOd as shown by the subjoined data obtained on: acornpound of the following composition:

Parts by weight Coprecipitated polymer blend (described above) Channel Black (Kosmobile-66) 50 Zinc oxide 5 I stearic acid 11.0 Sulfur 2.0

Benz'othiazyl disulfide' (Altax) When cured at 287 F., the above compoundhad the following properties:

Time of (hire min min. 90 min Tensile Strength (#/sq'. in.) 3, 315

Elongation, Per Cent Modulus at 300% Modulus at 400%, Solvent Swell, Per

Increase);

After' immcrsionior 48 hours at room temperature in a 50-50 mixture of ASTM- #3 011- and 'ASTM #1 oil 20% aromatic);

' The oil resistant synthetie rubbery materials Which are plasticized by the polymerized diolefim oils in accordance with the present invention are the emulsion copolymers of a' major proportion of a conjugated diol'efin of from- 4 to 6 carbon atoms per molecule; preferably butadiene-I-B, pip'erylene} isoprene or dimethyl butad iene and a minor'proportion of an acrylic nitrile, preferably acrylonitr-ile, methacrylonitrile', or halogen ated acrylonitriles such as alpha chloro=acrylo nitrile and the like.- While'the'diolefin must-con: stitutethe preponderant amount of thepolymer izable material, it is ordinarily preferable to utilize monomeric mixtures of from 55 to about 85 parts of 'diolefin with 45' to about 15 parts of nitrile.

The copolymers of diolefin and nitrile are prepared, as is well known in the art, by emulsifying the monomeric material in from an equal to a two-fold quantity of Water utilizing a watersoluble soap or other surface active agent as an emulsifier, an oxygen-yielding polymerization catalyst such as hydrogen peroxide, alkali metal or ammonium persulfates and perborates and if desired, polymerization modifiers such as aliphatic mercaptans of at least six carbon atoms per molecule. Polymerization is ordinarily effected to about 20 to about 65 C. and is continued until the monomers are about '75 to converted to polymers. Other oil-resistant polymers to which the present invention is applicable are polyvinyl chloride, polyvinyl acetate, elastomers prepared by the condensation of ethylene dichloride with sodium tetrasulfide (Thiokol, GR-P) and the like.

These rubbery polymers are readily plasticized according to the present invention by adding thereto between 5 and about 50, preferably between 15 and 30 parts of oily diolefin polymers having a Staudinger molecular weight between about 10,000 and 20,000, or an intrinsic viscosity between about 0.1 and 0.8, preferably between 0.2 and 0.6. Further modification of properties can also be obtained by mixing the rubbery nitrile polymer, in addition to ordinary compounding and vulcanizing ingredients, with varying quantities of other high molecular Weight substances such as natural rubber, GR-S, GR-I or the like. Furthermore, certain complementary non-solvating plasticizers such as diethylene glycol phthalate, linseed oil polymer-gel, polybutene of proper molecular weight and the like may be used along with the polydiolefin oils which constitute the essential plasticizing ingredient of the present invention as described in the foregoing examples.

However, it will be understood that these examples are merely illustrations of the invention which is by no means limited thereto, but that numerous variations are possible without departing from the scope of the invention as defined in the appended claims.

It is claimed:

1. A vulcanizable composition of matter comprising 100 parts of solid, rubber-like emulsion copolymer of 85 to 60% of butadiene and 15 to 40% of acrylonitrile and, as a softening agent therefor, to 20 parts of viscous polymerized vinyl cyclohexene having a Staudinger molecular weight between 10,000 and 20,000.

2. A vulcanizable composition of matter comprising 100 parts of a solid, rubber-like emulsion copolymer of about 74% of butadiene with about 26% of acrylonitrile; about 20 parts of an oily thermally polymerized vinyl cyclohexene having a Staudinger molecular weight within the range of 8,000 and 20,000; about 75 parts of carbon black; about 5 parts of zinc oxide; about 1.5 parts of stearic acid; about 1.5 parts of sulfur and about 1 part of benzothiazyl disulfide.

3. An improved extrusion method which comprises mixing 100 parts of a solid, rubber-like emulsion copolymer of 85 to 60% of butadiene and 15 to 40% of acrylonitrile, with 5 to 40 parts of polymerized vinyl cyclohexene having a Staudinger molecular weight between 10,000 and 20,000 and passing the resulting mixture through an extrusion zone at a temperature of about 220 F.

4. A vulcanizable composition of matter comprising 100 parts of a solid, rubber-like emulsion 12 copolymer of 85 to 60% of butadiene and 15 to 40% of acrylonitrile and, as a softening agent therefor, 5 to 20 parts of viscous polymer of vinyl cyclohexene having a molecular weight between 10,000 and 15,000 prepared by heating vinyl cyclohexene at 280 to 300 C. and separating the viscous polymer from the reaction product by extraction with methyl ethyl ketone.

ALBERT M. GESSLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,475,234 Gleason et a] July 5, 1949 2,500,983 Frolich et a1 July 5, 1949 FOREIGN PATENTS Number Country Date 492,998 Great Britain Sept. 30, 1938 705,104 Germany Apr. 17, 1941 OTHER REFERENCES Rubber Age (U. S.), August 1945, pp. 565, 568, 569.

Rubber Age and synthetics (B12) Feb. 1946, pp. 321, 322.

Stocklin: Pages 51 and 58, Transactions, Inst. of Rubber Industry, vol. 15, June 1939.

Talalay et al.: Synthetic Rubber from Alcohol, pages 96-98; pub., 1945, by Interscience Pub, N. Y.

Ludwig et al.: India Rubber World, Oct. 1944, pages 55 and 56.

Gessler et al.: India Rubber World, May 1947, page 212.

B. I. O. s. Overall Report No. 7, Rubber Industry in Germany 1939-1945, page 26; pub. in London, 1948. 

1. A VULCANIZABLE COMPOSITION OF MATTER COMPRISING 100 PARTS OF SOLID, RUBBER-LIKE EMULSION COPOLYMER OOF 85 TO 60% OF BUTADIENE AND 15 TO 40% OF ACRYLONITRILE AND, AS A SOFTENING AGENT THEREFOR, 5 TO 20 PARTS OF VISCOUS POLYMERIZED VINYL CYCLOHEXENE HAVING A STAUDINGER MOLECULAR WEIGHT BETWEEN 10,000 AND 20,000. 